We propose to develop an advanced dense sensor array electroencephalographic (EEG) system that is optimized for integration with whole-head magnetoencephalographic (MEG) systems. Electromagnetic measures have adequate temporal resolution for both neuropsychological and neurophysiological studies of aging. Hemodynamic neuroimaging methods (PET, fMRI) rely on blood flow changes that are too slow to track dynamic cognitive processes. Even when measures of abstract cognition, memory, or flexibility show no effects of normal aging, the older person is consistently found to be slower than the young person. Relating neuroanatomical deficits to cognitive function requires a neuroimaging technology to with good temporal resolution. We introduce a 256-channel sensor net that achieves low magnetic noise with carbon-fiber electrodes and a physiological amplifier that is engineered for high scalp impedance sensors and low magnetic interference. Most importantly, we propose a fully electromagnetic signal analytic strategy, in which the differing advantages of electrical and magnetic fields are combined within a single turnkey software package. Although the initial electromagnetic neuroimaging system would be sold initially to research laboratories, advances in understanding the changes in the time course of mental operations in the aged brain will have significant clinical applications. PROPOSED COMMERCIAL APPLICATIONS: By tracking neurophysiological slowing with millisecond precision, dense array MEG/EEG could optimize our understanding of neurological disorders of the aged, leading to accurate assessment of dementing illness when treatment is still useful.